1. Field of the Invention
Apparatuses and methods consistent with the present general inventive concept relate to a fusing roller which heats non-fused image transferred onto a printing medium and a method of manufacturing the same, a fusing unit employing the fusing roller and an image forming apparatus employing the fusing unit, and more particularly, to a fusing roller which is provided to prevent wrap jam, to secure heat necessary to fuse during a high-speed printing and a stable durability and a method of manufacturing the same, a fusing unit employing the fusing roller and an image forming apparatus employing the fusing unit.
2. Description of the Related Art
In general, an electrophotographic image forming apparatus scans a beam onto a photosensitive body electrified to a predetermined electric potential to form an electrostatic latent image, and develops the image with a predetermined color toner and transfers and fuses the same onto a printing medium to print an image thereon. The electrophotographic image forming apparatus is provided with a fusing unit along a printing path to fuse the transferred image onto the printing medium.
FIG. 1 is a schematic view illustrating a conventional lamp heating type fusing unit, and FIG. 2 is a schematic sectional view illustrating a layer configuration of a fusing roller in FIG. 1.
Referring to the figures, the conventional fusing unit is provided to fuse a non-fused toner image T formed on a printing medium M. The conventional fusing unit comprises a fusing roller 10 in which a thermal lamp 1 is built therein, a pressing roller 20 which is disposed to face the fusing roller 10 and is elastically biased to press toward the fusing roller 10 by an elastic member 5 to form a fusing nip, and a temperature sensor 7 which senses temperature of a surface of the fusing roller 10.
The fusing roller 10 comprises a first core pipe 11 which is provided of a metal material. A first elastic layer 15 and a first release-layer 19 (FIG. 2) are sequentially formed on the surface layer of the first core member 11 and jointed adhesively all together by primers 13 and 17 (FIG. 2).
Accordingly, the first core pipe 11 is heated by the thermal lamp 1, and the first elastic layer 15 is heated by a thermal conduction of the heated pipe 11 to rise to a predetermined fusing temperature where it is maintained.
The temperature sensor 7 measures temperature of a surface of the first elastic layer 15 in and out of contact with the fusing roller 10. Accordingly, a power supplied for the thermal lamp 1 can be controlled on the basis of the measured temperature value.
Accordingly, if the printing medium M on which the non-fused toner image T is formed is transferred to the fusing unit, the toner image T is heated and pressurized by passing through the fusing nip provided between the fusing roller 10 and the pressing roller 20, to be fused onto the printing medium M, and thus the fusing process is completed.
In the color electrophotographic image forming apparatus employing the fusing unit, a first elastic layer is required to have a thin thickness in order to improve warm-up efficiency in forming the fusing roller. Meanwhile, if the thickness of the first elastic layer is thin, a fusing property may be degraded due to reduction of the width of the fusing nip.
Therefore, a hardness of rubber which forms the first elastic layer must be in a low state in order to reduce a warm-up time, to secure fixedness, and to satisfy a margin for preventing wrap jam.
Meanwhile, as described above, if the hardness of the first elastic layer is low, the first elastic layer may be easily exfoliated from a first core pipe. The exfoliation phenomenon is deepened as the fusing temperature and pressure become high.
The exfoliation phenomenon is mainly caused by a chemical property of a low hardness rubber. This is because the low hardness rubber has a small number of cross-linked points, and accordingly is not easily jointed with material other than a high hardness rubber having a lot of cross-linked points. In particular, if the surface is relatively stabilized and does not have a reaction radical, a chemical reaction necessary for coupling tends to be insufficient or weak.
Also, the exfoliation phenomenon may be progressed to occur at a weak portion by a non-uniform coupling on a coupling surface between an elastic layer of rubber material having relatively high temperature and a high deformation and a metal core pipe.
Accordingly, the first elastic layer is exfoliated from the first core pipe under a fusing circumstance of a high temperature and high pressure, and thus durability of the fusing roller may be degraded.